What action is used to assess scapulohumeral rhythm at the scapula or scapulothoracic joint?

Scapulohumeral rhythm refers to the coordinated movement between the scapula and the humerus during arm elevation. Specifically, it is an important movement pattern that allows the shoulder girdle to effectively move in relation to the arm. When assessing scapulohumeral rhythm, abduction of the arm serves as an ideal action because it involves the simultaneous movement of the scapula upward and outward while the humerus moves away from the body.

During abduction, the scapula needs to rotate upward to allow for optimal range of motion of the shoulder joint. This action involves the contribution of various muscles, such as the trapezius and serratus anterior, which facilitate the necessary movements at the scapulothoracic joint. This rhythm is crucial for ensuring that the humeral head is properly positioned within the glenoid cavity of the scapula as the arm moves, thereby preventing impingement and promoting overall shoulder function.

While actions like adduction, flexion, and internal rotation may engage shoulder and scapular muscles, they do not specifically target the assessment of how the scapula and humerus synchronize their movements during elevation. Therefore, abduction is the most appropriate choice for assessing scapulohumeral rhythm, as it directly evaluates the relationship